Organophosphorus-modified zeolites and method of preparation

ABSTRACT

High VI lube oils are obtained in high yields when lower olefins are polymerized over an aluminosilicate HZSM-5 type catalyst or zeolite beta whose surface Bronsted acid sites have been inactivated with a sterically hindered basic organophosphorus compound.

REFERENCE TO COPENDING APPLICATION

This is a continuation-in-part of application Ser. No. 808,973, filedDec 16, 1985, now U.S. Pat. No. 4,658,079, which is acontinuation-in-part of U.S. patent application Ser. No. 709,143, filedMar 7, 1985, now U.S. Pat. No. 4,568,786, which is acontinuation-in-part of U.S. patent application Ser. No. 598,139, filedApr 9, 1964, now U.S. Pat. No. 4,520,221, incorporated herein byreference.

Field of the Invention

The invention relates to selective crystalline silicate catalystmaterial which is surface inactivated. These materials are useful forproducing high viscosity index lubricant range hydrocarbons from a lowerolefin feedstock.

BACKGROUND OF THE INVENTION

Recent work in the field of olefin upgrading has resulted in a catalyticprocess for converting lower olefins to heavier hydrocarbons. Heavydistillate and lubricant range hydrocarbons can be synthesized overZSM-5 type catalysts at elevated temperature and pressure to provide aproduct having substantially linear molecular conformations due to theellipsoidal shape selectivity of certain medium pore catalysts.

Conversion of olefins to gasoline and/or distillate products isdisclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank andRosinski) wherein gaseous olefins in the range of ethylene to pentene,either alone or in admixture with paraffins are converted into anolefinic gasoline blending stock by contacting the olefins with acatalyst bed made up of a ZSM-5 type zeolite. Particular interest isshown in a technique developed by Garwood, et al., as disclosed inEuropean Patent Application No. 83301391.5, published 29 Sept. 1983. InU.S. Pat. Nos. 4,150,062; 4,211,640; 4,227,992; and 4,547,613 Garwood etal disclose the operating conditions for the Mobil Olefin toGasoline/Distillate (MOGD) process for selective conversion of C₃ ⁺olefins to mainly aliphatic hydrocarbons.

In the process for catalytic conversion of olefins to heavierhydrocarbons by catalytic oligomerization using a medium pore shapeselective acid crystalline zeolite, such as ZSM-5 type catalyst, processconditions can be varied to favor the formation of hydrocarbons ofvarying molecular weight. At moderate temperature and relatively highpressure, the conversion conditions favor C₁₀ ⁺ aliphatic product. Lowerolefinic feedstocks containing C₂ -C₈ alkenes may be converted; however,the distillate mode conditions do not convert a major fraction ofethylene. A typical reactive feedstock consists essentially of C₃ -C₆mono-olefins, with varying amounts of nonreactive paraffins and the likebeing acceptable components.

SUMMARY OF THE INVENTION

It has been discovered that surface-inactivated internally active,metallosilicate medium pore zeolites may be produced by treatment withbulky organophosphorus base. It is a main object of this invention toprovide an improved catalyst useful in shape selective reactions, suchas upgrading olefins to lubricant product. Significantly improvedproduct linearity can be achieved by employing a catalyst comprising amedium pore or larger pore shape selective siliceous zeolite with asurface that has been substantially inactivated with a stericallyhindered basic organophosphorus compound or a sterically hinderedorganophosphonium cation.

Although it is known to use basic materials to deactivate the Bronstedacid sites on the surface of aluminosilicate catalysts, see U.S. Pat.No. 4,520,221 to C.S.H. Chen, incorporated herein by reference; thebasic materials employed are bulky amines such as alkylpyridines. Thebasic organophosphorus compounds, which include phosphines andquaternary phosphonium cations, are excellent surface-modifying agentsbecause they bind tightly to the Bronsted acid sites on thealuminosilicates, giving a more thermally stable catalyst.

DESCRIPTION

Several techniques may be used to increase the relative ratio ofintra-crystalline acid sites to surface active sites. This ratioincreases with crystal size due to geometric relationship between volumeand superficial surface area. Deposition of carbonaceous materials bycoke formation can also shift the effective ratio as disclosed in U.S.Pat. No. 4,547,613. However, enhanced effectiveness is observed wherethe surface acid sites of small crystal zeolites are reacted with achemisorbed basic organophosphorus compound.

Zeolite catalysts can be surface inactivated in situ by cofeeding asterically hindered basic organophosphorus compound with processfeedstock and/or the catalyst can be treated in a separate step prior toconversion use.

Shape-selective oligomerization, as it applies to the conversion of C₂-C₁₀ olefins over ZSM-5, is known to produce higher olefins up to C₃₀and higher. As reported by Garwood in Intrazeolite Chemistry 23, (Amer.Chem. Soc., 1983), reaction conditions favoring higher molecular weightproduct are low temperature (200-260° C.), elevated pressure (about 2000kPa or greater), and long contact time (less than 1 WHSV). The reactionunder these conditions proceeds through the acid-catalyzed steps of (1)oligomerization, (2) isomerization-cracking to a mixture of intermediatecarbon number olefins, and (3) interpolymerization to give a continuousboiling product containing all carbon numbers. The channel systems ofZSM-5 type catalysts impose shape-selective constraints on theconfiguration of the large molecules, accounting for the differenceswith other catalysts.

The desired oligomerization-polymerization products include C₁₀ ⁺substantially linear aliphatic hydrocarbons. The ZSM-5 catalytic pathfor propylene feed provides a long chain with approximately one loweralkyl (e.g. methyl) substituent per 8 or more carbon atoms in thestraight chain.

The final molecular configuration is influenced by the pore structure ofthe catalyst. For the higher carbon numbers, the structure is primarilya methyl-branched straight olefinic chain, with the maximum crosssection of the chain limited by the 5.4×5.6 Angstrom dimension of thelargest ZSM-5 pore. Although emphasis is placed on the normal 1-alkenesas feedstocks, other lower olefins such as 2-butene or isobutylene, arereadily employed as starting materials due to rapid isomerization overthe acidic zeolite catalysts. At conditions chosen to maximize heavydistillate and lubricant range products (C₂₀ ⁺) the raw aliphaticproduct is essentially mono-olefinic. Overall branching is notextensive, with most branches being methyl at about one branch per eightor more atoms.

The viscosity index of a hydrocarbon lube oil is related to itsmolecular configuration. Extensive branching in a molecule usuallyresults in a low viscosity index. It is believed that two modes ofoligomerization/polymerization of olefins can take place over acidiczeolites such as HZSM-5. One reaction sequence takes place at Bronstedacid sites inside the channels or pores, producing essentially linearmaterials. The other reaction sequence occurs on the outer surface,producing more branched material. By decreasing the surface acidactivity (surface α-value) of such zeolites, fewer highly branchedproducts with low VI are obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless otherwise specified, metric units and parts-by-weight (pbw) areutilized in the description and examples.

The shape-selective oligomerization/polymerization catalysts preferredfor use herein include the crystalline aluminosilicate zeolites having asilica to alumina molar ratio of at least 12, a constraint index ofabout 0.5 to 12 and acid cracking activity of about 50-400.Representative of the ZSM-5 type zeolites are ZSM-5, ZSM-11, ZSM-12,ZSM-22, ZSM-23, ZSM-35 and ZSM-38. ZSM-5 is disclosed and claimed inU.S. Pat. No. 3,702,886 and U.S. Pat. No. Re. 20,948; ZSM-11 isdisclosed and claimed in U.S. Pat. No. 3,709,979. Also, see U.S. Pat.No. 3,832,449 for ZSM-12; U.S. Pat. No. 4,076,842 for ZSM-23; U.S. Pat.No. 4,016,245 for ZSM-35 and U.S. Pat. No. 4,046,839 for ZSM-38. Thedisclosures of these patents are incorporated herein by reference. Asuitable shape selective medium pore catalyst for fixed bed is a smallcrystal H-ZSM-5 zeolite (silica:alumina ratio=70:1) with alumina binderin the form of cylindrical extrudates of about 1-5 mm. A large poreshape selective catalyst is a small crystal zeolite beta (silica aluminaratio=40:1) with alumina binder. Unless otherwise stated in thisdescription, the catalyst shall consist essentially of ZSM-5, or zeolitebeta which has a crystallite size of about 0.02 to 0.05 micron. Otherpentasil catalysts which may be used in the primary or secondary reactorstages include a variety of medium to large pore (˜5 to 8A) siliceousmaterials such as gallo-silicates, ferrosilicates, and/oraluminosilicates disclosed in U.S. Pat. Nos. 4,414,413 and 4,417,088 and3,308,069 (U.S. Pat. No. Re. 28,341), incorporated herein by reference.

The members of the class of zeolites useful herein have an effectivepore size of generally from about 5 to about 8 angstroms, such as tofreely sorb normal hexane. In addition, the structure must provideconstrained access to larger molecules. It is sometimes possible tojudge from a known crystal structure whether such constrained accessexists. For example, if the only pore windows in a crystal are formed by8-membered rings of silicon and aluminum atoms, then access by moleculesof larger cross-section than normal hexane is excluded and the zeoliteis not of the desired type. Windows of 10-membered rings are preferred,although, in some instances, excessive puckering of the rings or poreblockage may render these zeolite ineffective.

Although 12-membered rings in theory would not offer sufficientconstraint to produce advantageous conversions, it is noted that thepuckered 12-ring structure of TMA offretite does show some constrainedaccess. Other 12-ring structures may exist which may be operative forother reasons, and therefore, it is not the present intention toentirely judge the usefulness of the particular zeolite solely fromtheoretical structural considerations.

A convenient measure of the extent to which a zeolite provides controlto molecules of varying sizes to its internal structure is theConstraint Index of the zeolite. Zeolites which provide a highlyrestricted access to and egress from its internal structure have a highvalue for the Constraint Index, and zeolites of this kind usually havepores of small size, e.g. less than 5 angstroms. On the other hand,zeolites which provide relatively free access to the internal zeolitestructure have a low value for the Constraint Index, and usually poresof large size, e.g. greater than 8 angstroms. The method by whichConstraint Index is determined is described fully in U.S. Pat. No.4,016,218, incorporated herein by reference for details of the method.

Constraint Index (CI) values for some typical materials are:

    ______________________________________                                                        CI     (at test temperature)                                  ______________________________________                                        ZSM-4             0.5      (316° C.)                                   ZSM-5 (crystal size -                                                                           6-8.3    (371° C.-316° C.)                    0.2 to 0.5 microns)                                                           ZSM-5 (crystal size -                                                                           7.2-13.3 (250° C.)                                   1-2 microns)                                                                  ZSM-11            5-8.7    (371° C.-316° C.)                    ZSM-12            2.3      (316° C.)                                   ZSM-20            0.5      (371° C.)                                   ZSM-22            7.3      (427° C.)                                   ZSM-23            9.1      (427° C.)                                   ZSM-34            50       (371° C.)                                   ZSM-35            4.5      (454° C.)                                   ZSM-38            2        (510° C.)                                   ZSM-48            3.5      (538° C.)                                   ZSM-50            2.1      (427° C.)                                   TMA Offretite     3.7      (316° C.)                                   TEA Mordenite     0.4      (316° C.)                                   Clinoptilolite    3.4      (510° C.)                                   Mordenite         0.5      (316° C.)                                   REY               0.4      (316° C.)                                   Amorphous Silica-alumina                                                                        0.6      (538° C.)                                   Dealuminized Y    0.5      (510° C.)                                   Erionite          38       (316° C.)                                   Zeolite Beta      0.6-2.0  (316° C.-399° C.)                    ______________________________________                                    

The above-described Constraint Index is an important definition of thosezeolites which are useful in the instant invention. The very nature ofthis parameter and the recited technique by which it is determined,however, admit of the possibility that a given zeolite can be testedunder somewhat different conditions and thereby exhibit differentConstraint Indices. Constraint Index seems to vary somewhat withseverity of operations (conversion) and the presence or absence ofbinders. Likewise, other variables, such as crystal size of the zeolite,the presence of occluded contaminants, etc., may affect the ConstraintIndex. Therefore, it will be appreciated that it may be possible to soselect test conditions, e.g. temperature, as to establish more than onevalue for the Constraint Index of a particular zeolite. This explainsthe range of Constraint Indices for some zeolites, such as ZSM-5, ZSM-11and Beta.

It is to be realized that the above CI values typically characterize thespecified zeolites, but that such are the cumulative result of severalvariables useful in the determination and calculation thereof. Thus, fora given zeolite exhibiting a CI value within the range of 0.5 to 12,depending on the temperature employed during the the test method withinthe range of 290° C. to about 538° C., with accompanying conversionbetween 10% and 60%, the CI may vary within the indicated range of 0.5to 12 prior to surface treatment. Likewise, other variables such as thecrystal size of the zeolite, the presence of possibly occludedcontaminants and binders intimately combined with the zeolite may affectthe CI. It will accordingly be understood to those skilled in the artthat the CI, as utilized herein, while affording a highly useful meansfor characterizing the zeolites of interest is approximate, taking intoconsideration the manner of its determination, with the possibility, insome instances, of compounding variable extremes. However, in allinstances, at a temperature within the above-specified range of 290° C.to about 538° C., the CI will have a value for any given untreatedzeolite of interest herein within the approximate range of 0.5 to 12. Ithas been found that surface treatement with the bulky organophosphorusbases can increase the C.I. measurement by 20% or more. While thisphenonenon is not fully understood, modification of pore structure maybe effected. Such increase in constraint has not been previously known.For example, the C.I. for HZSM-5 can be increased from less than 10 upto about 40 by the novel phosphorus treatment technique.

It is generally understood that the proportion of internal acid sitesrelative to external acid sites increases with larger crystal size.However, the smaller crystallites, usually less than 0.1 micron, arepreferred for diffusion-controlled reactions such as oligomerization,polymerization, etc. Accordingly, it may be required to neutralize morethan 15% of the total Bronsted acid sites by chemisorption of the basicdeactivating agent.

The degree of steric hindrance should also be considered in the choiceof the basic organophosphorus compounds, especially the bulky quaternaryphosphonium species. Although the selected organophosphorus compoundmust be bulky enough to prevent infusion of said compound into theinternal pores of the catalyst, excessive steric hindrance may preventeffective or complete interaction between the surface Bronsted acid siteand the selected basic species.

Catalysts of low surface activity can be obtained by using medium orlarger pore zeolites of small crystal size that have been deactivated bybasic organophosphorus compounds such as phosphines or quaternaryphosphonium salts. These compounds all must have a minium cross sectiondiameter greater than the effective pore size of the zeolite to betreated; i.e., greater than 5 Angstroms for a ZSM-5 type zeolite, andgreater than 7.5 Angstroms for zeolite Beta.

EXAMPLE I

Aluminosilicate HZSM-5 particles, having an average crystal size ofabout 0.02 to 0.05 micron, are mixed with a solution (1%) oftriphenylphosphine in hexane at room temperature for four days. Thetreated catalyst particles are then filtered, washed, and dried in anoven at 110° C. The dried product is quantitated against a standardcompound (butyltriphenylphosphonium bromide) and it was determined that2380 ppm phosphorus is chemisorbed on the catalyst particles. Thisamount of phosphorus corresponds to a basic exchange of 16.2% of all theAl acid sites on the catalyst.

The above-described treated catalyst particles are then tested foracid-catalyzed cracking reactions which will occur only on the surfaceof said catalyst. A feed of sterically-hindered1,3,5-tri-tert-butylbenzene is passed over the treated HZSM-5 catalystunder standard cracking conditions of temperature and pressure. Themolecule of 1,3,5-tri-tert-butylbenzene is geometrically too bulky toenter the internal pores of the catalyst, and thus can undergo crackingonly on the surface of the catalyst. The results of the experimentconfirm that no cracking reaction takes place, indicating that thetreated HZSM-5 catalyst is surface-inactivated. The unmodified ZSM-5 istested for constraint at 250° C., giving C.I. values of 6.4, 8.4, 9.6and 9.6 at hexane cracking reaction times of 20, 50, 60 and 8 minutes,respectively. The corresponding values for the surface treated zeoliteare 12.7, 13.0, 16.8 and 13.9 (83 min.)

EXAMPLE II

The surface-inactivated catalyst is prepared in the same manner asExample I except that the catalyst particles are a mixture of 65% HZSM-5and 35% Al₂ O₃. The amount of phosphorus chemisorbed on the catalyst is1610 ppm.

EXAMPLE III

The surface-inactivated catalyst is prepared in the same manner asExample I except that the surface-modifying solution for treating theHZSM-5 catalyst particles is a solution (1%) ofbutyltriphenylphosphonium bromide in water. The amount of phosphoruschemisorbed on the catalyst is 350 ppm, which corresponds to a basicexchange of 2.3% of all the Al acid sites.

Despite the fact that not all of the surface acid sites on the catalystare neutralized, the treated catalyst shows no cracking activity when1,3,5-tri-tert-butylbenzene is employed as the feed.

EXAMPLE IV

The surface-inactivated catalyst is prepared in the same manner asExample I except that the surface-neutralizing solution for treating theHZSM-5 catalyst particles is a solution (1%) of tetraphenylphosphoniumbromide. The amount of phosphorus chemisorbed on the catalyst was 410ppm, which corresponds to a basic exchange of 2.7% of all the Al acidsites. The treated catalyst shows no activity under cracking conditionswhen 1,3,5-tri-tert-butylbenzene is employed as the feed. The C.I. valueis increased from approximate 6-10 range to values of 40.1 (20 min.),36.9 (40 min.), 20.6 (64 min.) and 15.4 (85 min).

EXAMPLE V

The surface-inactivated catalyst is prepared in the same manner asExample I except that the surface-neutralizing solution for treating theHZSM-5 catalyst particles is a solution (1%) of tetrabutylphosphoniumbromide. The treated catalyst shows no activity under crackingconditions when 1,3,5-tri-tert-butylbenzene is employed as the feed.

EXAMPLE VI

The surface-inactivated catalyst is prepared in the same manner asExample I except that the surface-neutralizing solution for treating theHZSM-5 catalyst particles is a solution (1%) of tetraethylphosphoniumchloride in water, and the mixing of catalyst and saline solution occursfor 6 days. The treated catalyst exhibits no cracking activity when abulky feedstock such as 1,3,5-tri-tert-butylbenzene is employed.

EXAMPLE VII

The catalyst is prepared in the same manner as Example I except that thesolution for treating the HZSM-5 catalyst particles is a solution (1%)of tetramethylphosphonium chloride in water. The amount of phosphoruschemisorbed on the catalyst is 3620 ppm, which corresponds to a basicexchange of 24.7% of all the Al acid sites. However, cracking occurswhen the treated catalyst is contacted with1,3,-5-tri-tert-butylbenzene. There are still active Al acid sites onthe surface of the treated catalyst because the tetramethylphosphiumions, due to their smaller size, can migrate inside the zeolite pores.Therefore, an amount of internal Al acid sites are neutralized as wellas an amount of surface Al acid sites. The remaining active surface Alacid sites are responsible for cracking the highly-branched feedstock.

EXAMPLE VIII

The surface-inactivated catalyst is prepared in the same manner asExample IV except that the catalyst particles are aluminosilicatezeolite Beta. The surface-modified catalyst shows no cracking activitywhen 1,3,5-tri-tert-butylbenzene is employed as the feedstock to apressure reactor.

EXAMPLE IX Lube Oil Preparation

A feedstock comprising 55 parts by weight propylene is charged to apressure reactor containing 5 parts of untreated zeolite HZSM-5particles as catalyst under inert atmosphere. When the reactor washeated to 230° C, the pressure was 6300 kPa (920 psi). After 5.2 hours,the pressure decreases to about 900 kPa (100 psi), and then to about 380kPa (55 psi). After 43 hours GC analysis shows that the pale yellowproduct comprises a lube oil composition boiling at 343° C.⁺ (650° F.⁺)and having a viscosity index of 72. The overall yield of lube oil (343°C.⁺) is 28.2%.

EXAMPLE X Lube Oil Preparation

The surface-inactivated catalyst of Example I is employed in a pressurereactor in an inert atmosphere for contacting a feedstock of propyleneat 230° C. (446° F.). The ambient propylene pressure starts at 8108 kPa(1180 psi). After 19 hours, the pressure is decreased to about 1920 kPa(280 psi), and then to 275 kPa (40 psi) after 74 hours. The finalproduct consists of lube oil (343° C.⁺) and lower boiling hydrocarbonliquids. Upon distillation, the nearly colorless lube oil (343° C.⁺) isfound to have a viscosity index of 147. The overall yield of lube oil is7.4%.

EXAMPLE XI

The surface-inactivated catalyst and propylene feed of Example IV areemployed in a pressure reactor at 230° C. (446° F.). The initial ambientpressure is about 8100 kPa (1180 psi). During the polymerization, thepressure continually decreases until it reaches a value of about 400 kPa(60 psi) after four days. The final product is a nearly colorless liquidcontaining a lube oil (343° C.⁺) and lower boiling hydrocarbons. Upondistillation, the lube oil is found to have a viscosity index of 132.The overall yield of the lube oil is 19% after 8 days.

EXAMPLE XII Lube Oil Preparation

The surface-inactivated catalyst and propylene feed of Example VIII areemployed in a pressure reactor at 230° (446° F.). The initial pressureis 7150 kPa (1040 psi). During the polymerization, the pressure dropsuntil it reaches a value of about 450 kPa (65 psi) after 6 days. Thefinal product is a pale yellow liquid containing a lube oil fraction(343° C.⁺) and lower boiling hydrocarbons. Upon distillation, the lubeoil fraction (calculated yield of 14.4%) is found to have a viscosityindex of 153.

Multi-stage processing

The present invention may be employed advantageously in staged reactorswherein lower olefins (e.g. C₂ -C₄) are upgraded to a substantiallylinear intermediate olefin in a primary stage and further converted tolubricant range (C₂₀ ⁺) hydrocarbons in a second stage at elevatedpressure.

A lower olefinic feedstock, such as propene, butene, etc., is charged toa continuously operated series of fixed bed downflow reactors containingan amount of aluminosilicate HZSM-5 catalyst or related species such aszeolite beta. In combination with the lower olefinic feedstock, there isadded to the first reactor, an amount of a sterically-hinderedorganophosphorus basic material, such as phosphines, said basic materialbeing mixed with the feed at a rate sufficient to maintain surfaceinactivity in the catalyst. Quaternary phosphonium compounds which donot elute with the feed and hydrocarbon products are particularlyuseful. The organophosphorus material must be sterically-hindered to thedegree that it will not enter the internal pores of the aluminosilicatecatalyst. Preferably, triphenylphosphine is injected into the feed at aconcentration of about 5 to 1000 ppm. The temperature within each of thedownflow reactors is controlled to remain within the bounds of about200° to 290° C. (392°-554° F.). While process pressure may be maintainedover a wide range, usually from about 2000 to over 20,000 kPa (300-3000psia), the preferred pressure is about 7000 to 15,000 kPa (1000 to 2000psia).

In a typical continuous process run under steady state conditions usingHZSM-5 catalyst, the average reactor temperature in the series ofadiabatic fixed bed reactors is maintained below about 260° C. (500°F.). In order to optimize formation of high molecular weight C₁₀ +hydrocarbons, effluent temperature from the terminal reactor is keptsubstantially below about 290° C. (554° F).

The effluent mixture from the primary reactor enters a high temperatureseparator, wherein high boiling product is recovered as a liquid rich inC₁₀ ⁺ hydrocarbons; while volatile components of the effluent stream,including light gas and lower hydrocarbons, such as C₁ to C₉ aliphaticsare recovered as a vapor stream. Preferably, the major portion (e.g. 50%to more than 90 wt %) of C₁₀ ⁺ hydrocarbon components are contained inthe high boiling liquid fraction. Overhead vapor is withdrawn through aconduit, cooled indirectly by incoming feedstock in a heat exchanger tocondense a major amount of C₅ -C₉ gasoline range hydrocarbons forrecovery. This condensed stream provides essentially all of the liquidolefinic recycle stream for combination with the feedstock.Advantageously, the major portion of C₅ to C₉ hydrocarbon components arecontained in this liquified recycle stream; however, an optional recyclestream may be obtained from distilled raw gasoline. By controlling thereaction temperature, especially in the last bed, undesired cracking ofthe product C₁₀ ⁺ hydrocarbons is minimized. Advantageously, both stagescontain HZSM-5 catalyst and are operated continuously and/or batchwise.By contacting the primary stage heavy effluent fraction with an acidexchange resin or other adsorbent in a neutralizer between stages anyresidual organophosphorus base is removed. This step may not benecessary if no organophosphorus compound, such as the quaternaryphosphonium ions, is eluted.

The secondary reactor usually is maintained at an average temperatureless than about 260° C. at elevated pressure greater than about 2000 kPaand weight hourly space velocity less than 1 hr ⁻¹. An olefinicintermediate stream comprising C₁₀ ⁺ hydrocarbons is pressurized andheated prior to entering the secondary reactor for furtheroligomerization conversion to produce lubricant, raw olefinic gasoline,distillate, etc. The effluent may be cooled prior to flashing in a phaseseparator. Overhead containing gasoline, C₄ ⁻ light gas, and lightdistillate may be recovered as product and/or recycled to the reactorstage(s).

Advantageously, the effluent liquid stream from the secondary reactor isfractionated to provide a major raw product stream consistingessentially of 290° C.⁺ aliphatic hydrocarbons comprising a major amountof C₁₀ -C₂₀ distillate and C₂₀ -C₆₀ aliphatic hydrocarbons. This rawolefinic product may then be hydrotreated in a separate process step toprovide a paraffinic lubricant and/or heavy distillate product. Detailsof a mild hydrogenation treatment may be obtained from U.S. Pat. No.4,211,640, incorporated by reference, typically using Co or Ni with W/Moand/or noble metals. The hydrotreated stream may be further fractionatedto yield refined high grade lubricants of outstanding quality.

While the invention has been described by specific examples andembodiments, there is no intent to limit the inventive concept except asset forth in the following claims.

I claim:
 1. A surface-inactivated catalyst composition comprising amedium or large pore shape-selective siliceous zeolite material havingactive internal Bronsted acid sites and containing asurface-inactivating amount of an organophosphorus base or cation, thebase or cation having an effective cross section larger than the zeolitepore.
 2. The catalyst composition of claim 1 wherein said zeolitematerial comprises aluminosilicate having a silica-to-alumina mole ratioof at least 12 and a constraint index of about 0.5 to 12 prior tophosphorus compound surface treatment.
 3. The catalyst composition ofclaim 2 wherein the aluminosilicate consists essentially of HZSM-5having an acid cracking value of about 50 to 400 prior to treatment, andwherein surface acidity is neutralized by a quaternary phosphoniumcompound.
 4. The catalyst composition of claim 1 wherein theorganophosphorus base comprises at least one phosphine or phosphoniumcompound.
 5. The catalyst composition of claim 4 wherein theorganophosphorus compound comprises a tetraphenyl phosphonium salt. 6.The catalyst of claims 1 and 2 wherein the zeolite material comprisesZSM-5 type zeolites or zeolite beta.
 7. A method of making ashape-selective catalyst comprisingcontacting an acid medium porezeolite having the structure of ZSM-5 with a solution of anorganophosphorus deactivating agent to chemisorb said agent onto thezeolite surface for rendering said zeolite surface substantiallyinactive for acidic reaction, the deactivating agent comprising atertiary phosphine or quaternary phosphonium compound having aneffective cross-section greater than 5 Angstroms.
 8. Asurface-inactivated catalyst composition comprising a zeolite having thestructure of ZSM-5 and having active internal Bronsted acid sites andcontaining no metals other than periodic group IIIB or IVB elements andhaving an acid cracking value of greater than 50 and containing asurface-inactivating amount of an organophosphorus base or cation, saidbase or cation having an effective cross-section larger than a zeolitepore.
 9. The method of claim 7 wherein the zeolite catalyst having thestructure of ZSM-5 has a constraint index less than 10 prior totreatment with the deactivating agent and a constraint index greaterthan 12 following treatment.
 10. An improved medium pore siliceouszeolite material having internally active Bronsted acid sites and beingsurface inactivated by treatment with sufficient organophosphorus toincrease substrate material constraint index by at least 20%, theorganophosphorus having an effective cross-section larger than thezeolite pore.
 11. The zeolite material of claim 10 wherein the pore sizeis about 5 to 8 Angstroms, wherein the untreated substrate has aconstraint index less than 12, and the phosphorus-treated material has aconstraint index of about 12 to
 40. 12. The zeolite material of claim 11wherein the substrate consists essentially of zeolite having thestructure of ZSM-5 and containing no metals other than periodic groupIIIB or IVB elements.
 13. The zeolite material of claim 12 wherein thesubstrate consists essentially of aluminosilicate HZSM-5 having aconstraint Index of about 6 to 10.